Traditional laminates for printed circuits usually employ brominated flame retardants to achieve flame retardancy, and especially employ tetrabromobisphenol-A epoxy resin. Such brominated epoxy resin has good flame retardancy but generates hydrogen bromide gas when combusting. In addition, dioxin, dibenzofuran and other cancerogenic substances have been detected in combustion products of halogen (such as bromide and chloride, etc.)-containing electrical and electronic equipment wastes for the past few years, therefore the application of brominated epoxy resins is under restrictions. Two European Union environment-protecting directives of “waste electrical and electronic equipment” and “the restriction of the use of certain hazardous substances in electrical and electronic equipment” have been officially implemented on Jul. 1, 2006, and the development of halogen-free flame retardant copper-clad laminates has become a hot spot in the industry. Each copper-clad laminates manufacturer has sequentially introduced its own halogen-free flame retardant copper-clad laminates.
Meanwhile, along with high speed and multi-functionalization in information processing of electronic products, application frequency has been constantly increased. Besides maintaining increasingly high requirements for environment protection, dielectric constant and dielectric dissipation value are requested to be increasingly low. Accordingly, reducing Dk/Df has been a hot spot pursued by baseboard practitioners.
CN 101418205 discloses a halogen-free flame retardant adhesive and its application in prepreg and multilayer printed board. The adhesive consists of resin, organic phosphorus-containing flame retardant, inorganic filler, curing accelerator and solvent, wherein the resin is a composition consisting of 40-60 parts of benzoxazine resin, 15-20 parts of linear novolac resin, 20-45 parts of epoxy prepolymer, based on the parts by mass. The patent also discloses that the epoxy prepolymer is bisphenol-A epoxy resin, bisphenol-F epoxy resin, bisphenol-S epoxy resin or novolac epoxy resin, using linear novolac resin as a hardener. The adhesive possesses high glass transition temperature, high thermal resistance, high adhesion and low water absorption. However, along with high speed and multi-functionalization in consumer electronic information processing, the requirements of baseboard on glass transition temperature, thermal resistance, dielectric properties are becoming higher. The bisphenol-A epoxy resin, bisphenol-F epoxy resin, bisphenol-S epoxy resin have low glass transition temperature as well as poor thermal resistance and dielectric properties, and the novolac epoxy resin has high glass transition temperature and high thermal resistance but poor dielectric properties. Neither of them could meet the requirements on dielectric properties for high-speed areas laminates.